The present invention relates to light power-limiting devices, and more particularly, to a solar power-limiting passive device and to a method for limiting solar power transmission in windows. Employing absorption changes in a novel thermochromic composition, the responsivity of the composition is enhanced and the reaction time of the composition is shortened when exposed to solar light in the visible, near IR region, i.e., at wavelengths of about 0.3 to 2.5 micrometer (μm) of the optical spectrum and to IR imaging systems that employ focal plane arrays in various cameras exposed to infrared light in the 3 to 5 μm and 8 to 14 μm region of the optical spectrum. The additional response enhancing features in this invention enable the use of the thermochromic composition in places where efficient sunlight power limiting is essential and where low infrared emitting or “cold” objects are in the presence, in close vicinity, of high infrared emitting “hot” targets or background.
IR imaging systems employ focal plane arrays in various cameras, having focal plane detectors that are sensitive to light at the 3-5 and 8-12 μm ranges of the optical spectrum. The two ranges cover the two main windows in the IR transmission spectrum of the atmosphere. These systems need to be protected from dazzling and temporary or permanent damage caused by intense radiation sources in the field of view, yet the optical systems should at the same time be completely transparent at these wavelengths for low light power. The intense radiation sources may be of two kinds; first, coherent lasers in the spectral region, continuous or pulsed, and second, non-coherent sources like explosions, field-fire or hot substances in the field of view.